I have read that when accelerating from a full stop, it is better to accelerate briskly, but keeping the bar graph in the ECO zone, to cruising speed is better overall for gas mileage compared to accelerating slower and taking more time to reach cruising speed.... I have also heard that it is better to accelerate using the bar graph and making sure it only goes half an inch past the ECO display above it. This way uses less RPM. So I am totally confused...From experience, I would like to hear how you guys accelerate from a stop for the best mileage. Thanks!!
You can keep it at the top of the ECO bar When starting on an uphill incline, you can go into the power band.
I am no hypermiler by any means but I accelerate the way one person described as "the red bar tickles the far right hand side of the PWR zone". Where I live I have to do this just to keep up with existing traffic and not to impede anyone else's progress. I have found that I may lose more mpg during the acceleration or pulse phase but gain it back more quickly by getting up to speed quicker and thus gliding more quickly and for longer periods. You will find a lot of different variations and opinions on this topic, so experiment and pick the one that fits your driving style the best.
That is because it takes the same amount of work to accelerate you car to a given speed no matter how fast you accelerate. Your engine is more efficient at relatively high throttle openings.
Part Load Pumping Losses In A Spark Ignited IC Engine The Prius minimizes pumping losses in several ways: Atkinson engine makes less power so throttle is opened wider. Computer control can open throttle more than needed and save energy to battery Very light loads (those with the most pumping loss) can be battery driven.
If you accelerate "slowly" you might end up using more battery than necessary to compensate for the lower rpms of the ICE, although the computer will likely try to compensate within the torque request of the driver and a myriad of other factors. Battery is better used to glide with ICE off (when below 73km/h), than to move the car swiftly at a traffic light.
Ideally you don't want to use the battery during a glide either. Battery power is inefficient power. For gliding you want to use the kinetic energy stored in the moving mass of the car. Tom
I dont know all the fancy speak of engineers and gear-heads. Instead, I let other people try things and learn from them. In this case, the current (unofficial) world record Prius Hypermiler lists "brisk acceleration" as one of their techniques.
Well, if traffic and roads permit. Which is practically never in my case. The flow of traffic is pretty constant on specific roads I drive each day, so if I start gliding with no intervention of the electric motor I end up slowing down traffic. I need to keep a constant speed - I let the Prius decide what to do, I cannot (and I don't like, honestly speaking) pulse & glide... The only P&G I can do is between traffic lights I know the timing of. Otherwise my best fuel saver is predicting traffic trying to stop the car as much and as less abruptly as possible.
Allowing the Prius to do what is does is almost always the best policy. My reply did not relate to pulse and glide, but it does apply. You will note that the word "pulse" is nowhere mentioned. I was commenting on your statement that you like to glide with the assistance of the electric motor. Gliding is more efficient without using power from the battery. I suspect you are referring to cruising under electric power, where the motor allows you to maintain the speed of traffic without running the engine at inefficient loads. This mode better fits with your description. Tom
Yes - but that is what I almost never manage to do in my traffic situations... (hence my <50mpg personal average...) That's what I meant. Is that coasting? or AKA stealth mode? I think I need to come up with a collection of these names and add them to the Wiki...
I would call that stealth or EV mode. I think of coasting and gliding as having zero power consumption, so a gradual reduction in speed is required unless going downhill. Tom
Just as important as the acceleration rate is whether the Prius must shortly have to stop and lose all the kinetic energy created by the acceleration. When the Prius has to stop frequently and lose its kinetic energy, the Prius becomes less energy efficient. The amount of energy loss is roughly indicated by the speed from which the Prius must make a full stop at and how often it must stop. Hypermiling minimizes accelerating at speeds which would require stopping (lost of kinetic energy). To maximize the Prius fuel efficiency hypermiling minimize the lost of kinetic energy by avoiding speeds which would incur higher energy lost if the vehicle were required to stop AND minimizing the number of times the Prius needs to stop. . Assuming that the Prius does not have to stop anytime soon after accelerating from a full stop... Then fuel efficiency depends on the A. first 100-500 feet of road that the Prius must travel. Is it (1) downhill, (2) flat, or (3) uphill. B. What is the top speed that you are going to accelerate to? (1) under 25 mph (2) between 25mph to 45 mph (3) over 46 mph. C. Is your HV battery State of Charge (1) over 50% (2) under 50% D. Is your engine coolant temperature (1) under 160F, the first 50 minutes of driving a Prius in winter city driving and the first 25 minutes of winter highway driving. For summer time divide time in half. (2) over 160F, after driving the Prius for over 50 minutes in the winter city driving or or over 25 minute in winter highway driving. For the summer time divide time in half. IF A.(3) or B(3) or C.(1) or D.(1) THEN To start immediate press the Accelerator so that HSI display moves is pass *ECO* capsule midpoint approximately 3/4 to 5/6 of the way to on the *Eco" bar but not creating a "red" bar in the power range the middle of the ECO capsule. This will put you in the most efficent ICE burn mode possible while minimizing electricity usage. It will also warm up the Prius ICE. Only if the Prius is not able to reach the desired terminal velocity of X mph B.(3) should you press the accelerator harder and go into the power bar section ( > 2.0 GPH, > 2000 RPM ). Assuming that the Prius must accelerate from 0 mph at the bottom of the hill to a terminal velocity of X mph and it is desirable to maintain that speed to the top of the hill. Once X mph is achieve - throttle back the HSI to avoid accelerating over X mph. As you reach near the top of the hill slowly let go of the accelerator allow momentum to keep the Prius going. At very high speeds, its more fuel efficient to use Driving with Load (DWL) hypermiling technique which requires the driver fix the power on the HSI display via the accelerator and allow the speed of the Prius to drop/slowdown as the Prius climbs uphill. As the Prius reaches the top of the hill the foot is off the accelerator and the Prius is suppose to glide/coast on the crown of the hill. As the Prius starts to go downhill again, the accelerator is use to set the initial velocity and then the Prius is allow to glide (in Neutral ) down hill or coast downhill(in Drive - while charging the batteries if the Soc is low or barely using the electric motors in but not recharging the batteries). On a Flat road, there is also an option to do what's called a high speed pulse and glide. It works best when you have a tail wind and when the top speed is less than 55 mph. IF A.(1 or 2) or B.(1 or 2) or C.(1) or D.(2) Then press the accelerator so that the HSI indicator is about 1/8 to 3/8 of the way on the "ECo" bar to the left of the *ECO" capsule on the HSI until the Prius is between 12mph(flat road) to 25mph(downhill road). After which press the accelerator down further so the HSI indicator is 1/2 to 5/8 the way of the HSI indicator "ECO" bar this is the most fuel efficient setting to accelerate (1.5kilowatt power/.80 to 1.10 gallons per hour/1280rPm to 1480rpm) You get the best fuel efficiency when accelerating downhill. If A.(3) the downhill is very long and you don't need to recharge the HV batteries C.(1) then you can switch the transmissionto N(eutral) when the Prius reaches X mph - this removes the internal drag cause by the ICE but doesnot allow the HV batteris to recharge. before exiting the downhill put the transmission back into D(rive). IF A.(3) the downhill is very long and you need to recharge the HV batteries C.(2) then keep the Prius in D(rive) take your foot off the accelerator completely and the Prius was start recharging the HV battery pack. As you exit the downhill put your foot back on the accelerator making sure that the HSI is now in eco bar area and not in charge mode.
